#include<bits/stdc++.h>

using namespace std;

#define ll long long

int n,tn=,s,a,b;

struct apple{

    int y;

    bool operator<(apple that){

        return y<that.y;

    }

}app[];

int main(){

    scanf("%d%d",&n,&s);

    scanf("%d%d",&a,&b);

    for(int i=;i<n;i++){

        int tx,ty;

        scanf("%d%d",&tx,&ty);

        if(a+b>=tx){

            app[tn].y=ty;

            tn++;

        }

    }

    sort(app,app+tn);

    int cnt=;

    for(int i=;i<tn;i++){

        if(s>=app[i].y){

            s-=app[i].y;

            cnt++;

        }

        else{

            break;

        }

    }

    printf("%d\n",cnt);

}